jrtplib.h

最新的jrtplib

/**\mainpage JRTPLIB
 *
 * \author Jori Liesenborgs
 * \author Developed at the The Expertise Centre for Digital Media (EDM), a research 
 *         institute of the Hasselt University
 *
 * \section ack Acknowledgment
 *
 * 	I would like thank the people at the Expertise Centre for Digital Media
 * 	for giving me the opportunity to create this rewrite of the library.
 * 
 * \section intro Introduction
 * 	
 * 	This document describes JRTPLIB, an object-oriented
 * 	library written in C++ which aims to help developers in using the 
 * 	Real-time Transport Protocol (RTP) as described in RFC 3550.
 *
 * 	The library makes it possible for the user to send and receive data
 * 	using RTP, without worrying about SSRC collisions, scheduling and
 * 	transmitting RTCP data etc. The user only needs to provide the library
 *	with the payload data to be sent and the library gives the user access
 *	to incoming RTP and RTCP data.
 *
 *	\subsection idea Design idea
 *		
 *		The library provides several classes which can be helpful in
 *		creating RTP applications. Most users will probably need just the
 *		RTPSession class for building an application. This class
 *		provides the necessary functions for sending RTP data and handles
 *		the RTCP part internally.
 *
 *	\subsection changes Changes from version 2.x
 *
 *		One of the most important changes is probably the fact that this
 *		version is based on RFC 3550 and the 2.x versions were based upon
 *		RFC 1889 which is now obsolete.
 *
 *		Also, the 2.x series was created with the idea that the user would
 *		only need to use the RTPSession class which meant that the
 *		other classes were not very useful by themselves. This version on
 *		the other hand, aims to provide many useful components to aid the
 *		user in building RTP capable applications.
 *
 *		In this version, the code which is specific for the underlying
 *		protocol by which RTP packets are transported, is bundled in
 *		a class which inherits its interface from a class called
 *		RTPTransmitter. This makes it easy for different underlying
 *		protocols to be supported. Currently there is support for UDP over
 *		IPv4 and UDP over IPv6.
 *
 *		For applications such as a mixer or translator using the
 *		RTPSession class will not be a good solution. Other components can
 *		be used for this purpose: a transmission component, an SSRC table,
 *		an RTCP scheduler etc. Using these, it should be much easier to
 *		build all kinds of applications.
 * \section copyright Copyright license
 * 	
 * 	The library code uses the following copyright license:
 *
 * 	\code
 * Permission is hereby granted, free of charge, to any person
 * obtaining a copy of this software and associated documentation files
 * (the "Software"), to deal in the Software without restriction,
 * including without limitation the rights to use, copy, modify, merge,
 * publish, distribute, sublicense, and/or sell copies of the Software,
 * and to permit persons to whom the Software is furnished to do so,
 * subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY
 * KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
 * WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 * 	\endcode
 *
 * 	There are two reasons for using this license. First, since this is the
 * 	license of the 2.x series, it only seemed natural that this rewrite
 * 	would contain the same license. Second, since the RTP protocol is
 * 	deliberately incomplete RTP profiles can, for example, define additional
 * 	header fields. The best way to deal with this is to adapt the library
 * 	code itself and that's why I like to keep the license as free as
 * 	possible.
 *
 * \section starting Getting started with the RTPSession class
 * 	
 * 	To use RTP, you'll have to create an RTPSession object. The constructor
 * 	accepts one parameter, an instance of RTPMemoryManager. By default, no
 * 	memory manager will be used. For now, we'll keep it simple, so this is
 * 	our code so far:
 *
 * 	\code
 * RTPSession session; 
 * 	\endcode
 * 
 * 	To actually create the session, you'll have to call the Create member 
 * 	function which takes three arguments: the first one is of type RTPSessionParams 
 * 	and specifies the general options for the session. One parameter of this class 
 * 	must be set explicitly, otherwise the session will not be created successfully. 
 * 	This parameter is the timestamp unit of the data you intend to send and
 * 	can be calculated by dividing a certain time interval (in seconds) by the 
 * 	number of samples in that interval. So, assuming that we'll send 8000 Hz 
 * 	voice data, we can use this code:
 *
 * 	\code
 * RTPSessionParams sessionparams;
 *
 * sessionparams.SetOwnTimestampUnit(1.0/8000.0);
 * 	\endcode
 *
 * 	The other session parameters will probably depend on the actual RTP profile
 * 	you intend to work with. 
 *
 * 	The second argument of the Create function is a pointer to an RTPTransmissionParams 
 * 	instance and describes the parameters for the transmission component. The third
 * 	parameter selects the type of transmission component which will be used. By default,
 * 	an UDP over IPv4 transmitter is used, and for this particular transmitter, the
 * 	transmission parameters should be of type RTPUDPv4TransmissionParams. Assuming 
 * 	that we want our RTP portbase to be 8000, we can do the following:
 *
 * 	\code
 * RTPUDPv4TransmissionParams transparams;
 * 
 * transparams.SetPortbase(8000);
 * 	\endcode
 *
 * 	Now, we're ready to call the Create member function of RTPSession. The return 
 * 	value is stored in the integer \c status so we can check if something went 
 * 	wrong. If this value is negative, it indicates that some error occurred. 
 * 	A description of what this error code means can be retrieved by calling
 * 	RTPGetErrorString:
 *
 * 	\code
 * int status = session.Create(sessionparams,&transparams);
 * if (status < 0)
 * {
 *	std::cerr << RTPGetErrorString(status) << std::endl;
 *	exit(-1);
 * }
 *	\endcode
 *
 *	If the session was created with success, this is probably a good point 
 *	to specify to which destinations RTP and RTCP data should be sent. This is 
 *	done by a call to the RTPSession member function AddDestination. This 
 *	function takes an argument of type RTPAddress. This is an abstract 
 *	class and for the UDP over IPv4 transmitter the actual class to be 
 *	used is RTPIPv4Address. Suppose that we want to send our data to a 
 *	process running on the same host at port 9000, we can do the following:
 *	
 *	\code
 * uint8_t localip[]={127,0,0,1};
 * RTPIPv4Address addr(localip,9000);
 *
 * status = session.AddDestination(addr);
 * if (status < 0)
 * {
 *	std::cerr << RTPGetErrorString(status) << std::endl;
 *	exit(-1);
 * }
 * 	\endcode
 *
 * 	If the library was compiled with JThread support, incoming data is
 * 	processed in the background. If JThread support was not enabled at
 * 	compile time or if you specified in the session parameters that no
 * 	poll thread should be used, you'll have to call the RTPSession
 * 	member function Poll regularly to process incoming data and to send 
 * 	RTCP data when necessary. For now, let's assume that we're working 
 * 	with the poll thread enabled.
 *
 * 	Lets suppose that for a duration of one minute, we want to send
 * 	packets containing 20 ms (or 160 samples) of silence and we want
 * 	to indicate when a packet from someone else has been received. Also
 * 	suppose we have L8 data as defined in RFC 3551 and want to use
 * 	payload type 96. First, we'll set some default values:
 * 	
 * 	\code
 * session.SetDefaultPayloadType(96);
 * session.SetDefaultMark(false);
 * session.SetDefaultTimestampIncrement(160);
 * 	\endcode
 *
 * 	Next, we'll create the buffer which contains 160 silence samples
 * 	and create an RTPTime instance which indicates 20 ms or 0.020 seconds.
 * 	We'll also store the current time so we'll know	when one minute has 
 * 	passed.
 * 	
 * 	\code
 * uint8_t silencebuffer[160];
 * 
 * for (int i = 0 ; i < 160 ; i++)
 * 	silencebuffer[i] = 128;
 * 
 * RTPTime delay(0.020);
 * RTPTime starttime = RTPTime::CurrentTime();
 * 	\endcode
 *
 * 	Next, the main loop will be shown. In this loop, a packet containing
 * 	160 bytes of payload data will be sent. Then, data handling can
 * 	take place but this part is described later in the text. Finally,
 * 	we'll wait 20 ms and check if sixty seconds have passed:
 *	
 *	\code
 * bool done = false;
 * while (!done)
 * {
 * 	status = session.SendPacket(silencebuffer,160);
 * 	if (status < 0)
 * 	{
 * 		std::cerr << RTPGetErrorString(status) << std::endl;
 * 		exit(-1);
 * 	}
 * 	
 * 	//
 * 	// Inspect incoming data here
 * 	//
 * 	
 * 	RTPTime::Wait(delay);
 * 	
 * 	RTPTime t = RTPTime::CurrentTime();
 * 	t -= starttime;
 * 	if (t > RTPTime(60.0))
 * 		done = true;
 * }
 * 	\endcode
 *
 * 	Information about participants in the session, packet retrieval
 * 	etc, has to be done between calls to the RTPSession member
 * 	functions BeginDataAccess and EndDataAccess. This ensures that the 
 * 	background thread doesn't try to change the same data you're trying 
 * 	to access. We'll iterate over the participants 	using the 
 * 	GotoFirstSource and GotoNextSource member functions. Packets from 
 * 	the currently selected participant can be retrieved using the 
 * 	GetNextPacket member function which returns a pointer to an 
 * 	instance of the RTPPacket class. When you don't need the packet 
 * 	anymore, it has to be deleted. The processing of incoming data will 
 * 	then be as follows:
 * 	
 * 	\code
 * session.BeginDataAccess();
 * if (session.GotoFirstSource())
 * {
 * 	do
 * 	{
 * 		RTPPacket *packet;
 * 		while ((packet = session.GetNextPacket()) != 0)
 * 		{
 * 			std::cout << "Got packet with extended sequence number " 
 * 			          << packet->GetExtendedSequenceNumber() 
 * 					  << " from SSRC " << packet->GetSSRC() 
 * 					  << std::endl;
 * 			session.DeletePacket(packet);
 * 		}
 * 	} while (session.GotoNextSource());
 * }
 * session.EndDataAccess();
 *	\endcode
 *
 *	Information about the currently selected source can be obtained
 *	by using the GetCurrentSourceInfo member function of the RTPSession class. 
 *	This function returns a pointer to an instance of  RTPSourceData which 
 *	contains all information about that source: sender reports from that 
 *	source, receiver reports, SDES info etc. 
 *
 *	When the main loop is finished, we'll send a BYE packet to inform other 
 *	participants of our departure and clean up the RTPSession class. Also, 
 *	we want to wait at most 10 seconds for the BYE packet to be sent, 
 *	otherwise we'll just leave the session without sending a BYE packet.
 * 	
 * 	\code
 * delay = RTPTime(10.0);
 * session.BYEDestroy(delay,"Time's up",9);
 *	\endcode
 *	
 *	The complete code of the program is given in \c example2.cpp.
 *
 * \section errors Error codes
 *
 *	Unless specified otherwise, functions with a return type \c int
 *	will return a negative value when an error occurred and zero or a
 *  	positive value upon success. A description of the error code can
 *  	be obtained by using the RTPGetErrorString function, declared 
 *  	in rtperrors.h                                            
 * 
 * \section memory Memory management
 * 
 *	You can write you own memory manager by deriving a class from RTPMemoryManager.
 *	The following example shows a very basic implementation.
 *	
 *	\code
 * class MyMemoryManager : public RTPMemoryManager
 * {
 * public:
 *	MyMemoryManager() { }
 *	~MyMemoryManager() { }
 *	
 *	void *AllocateBuffer(size_t numbytes, int memtype)
 *	{
 *		return malloc(numbytes);
 *	}
 *
 *	void FreeBuffer(void *p)
 *	{
 *		free(p);
 *	}
 * };
 *	\endcode
 * 
 * 	In the constructor of RTPSession, you can specify that you would like to use
 * 	this memory manager:
 * 	
 * 	\code
 * MyMemoryManager mgr;
 * RTPSession session(&mgr);
 * 	\endcode
 *
 * 	Now, all memory allocation and deallocation will be done using the AllocateBuffer
 * 	and FreeBuffer implementations of \c mgr.
 *
 * 	The second parameter of the RTPMemoryManager::AllocateBuffer member function
 * 	indicates what the purpose is of this memory block. This allows you to handle
 * 	different kinds of data in different ways.
 *
 * 	With the introduction of the memory management system, the RTPSession class was
 * 	extended with member function RTPSession::DeletePacket and RTPSession::DeleteTransmissionInfo.
 * 	These functions should be used to deallocate RTPPacket instances and RTPTransmissionInfo
 * 	instances respectively.
 *
 * \section contact Contact
 *
 * 	If you have any questions, remarks or requests about the library or
 * 	if you think you've discovered a bug, you can contact me at
 * 	\c jori(\c dot)\c liesenborgs(\c at)\c gmail(\c dot)\c com
 *
 * 	The home page of the library is
 *	http://research.edm.uhasselt.be/jori/jrtplib/jrtplib.html
 *
 * 	There is also a mailing list for the library. To subscribe to the list, 
 * 	send an e-mail with the text \c subscribe \c jrtplib as the message body 
 * 	(not the subject) to \c majordomo(\c at)\c edm(\c dot)\c uhasselt(\c dot)\c be 
 * 	and you'll receive further instructions.
 */